Hardware Reference
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8
SBAU293 – March 2018
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Copyright © 2018, Texas Instruments Incorporated
ADS1261 and ADS1235 Evaluation Module
ADVANCE INFORMATION
(1)
J1 and J3 are not populated on the ADS1235EVM.
(2)
Analog inputs are pinned out to terminal blocks through RC filters. Refer to
Figure 14
for additional connection details.
Table 4. Analog Input Terminal Blocks, J1–J4
Pin
Function
Test Point
ADS1261 Input Pin
ADS1235 Input Pin
J1
(1)
1
(ADS1261EVM) Analog input
(2)
A9
AIN9
–
2
(ADS1261EVM) Analog input
(2)
A8
AIN8
–
J2
1
Analog input
(2)
A7
AIN7
AIN5
2
Analog input
(2)
A6
AIN6
AIN4
3
Analog input
(2)
A5
AIN5
AIN3
4
Analog input
(2)
A4
AIN4
AIN2
5
Analog input
(2)
A3
AIN3
AIN1
6
Analog input
(2)
A2
AIN2
AIN0
7
Analog input
(2)
A1
AIN1
REFN0
8
Analog input
(2)
A0
AIN0
REFP0
J3
(1)
1
(ADS1261EVM) Analog input
(2)
A10
AINCOM
–
2
(ADS1261EVM) Reference output
–
REFOUT
–
J4
1
GND
–
DGND
DGND
2
AVSS
–
AVSS
AVSS
3.2.2
External Clock
By default, a clock is supplied by the internal oscillator of the ADC when the CLKIN pin is pulled low.
However, the EVM also provides the capability to connect an external clock directly to the ADC using the
J6 connector (see
Figure 16
.) When connecting to J6, a direct connection can be made between pins 42
(CLKIN) and 40 (GND). A typical clock source of 7.3728 MHz (or 10.24 MHz for 40 kSPS mode, on the
ADS1261) will track with all timing shown in
ADS126x Precision, 5-Channel and 10-Channel, 40-kSPS,
24-Bit, Delta-Sigma ADCs With PGA and Voltage Reference
or
ADS1235 High-Resolution, 24-Bit, 7200-
SPS, Delta-Sigma, Analog-to-Digital Converter With Programmable Gain Amplifier for Bridge Sensors
.
NOTE:
The CLKIN pin connects to the Tiva microcontroller. The microcontroller holds the CLKIN pin
low in order to enable the internal oscillator of the ADC. Before applying an external clock,
be sure to disable the GPIO output on this pin by sending the "HOLDCLOCK 0" command,
described in
Table 7
.
